Even though you don't want to start leveling all over again.

You might try making one of your 70's the leader, and group with 2 new (same class) characters just to get the hang of it.

Doing this will get you started. You are going to spend a LOT of time with macros, especially if you play multiple classes.
But, In my opinion, that's part of the fun!

Also, you mention "I have accesses to 3 accounts". Are all the accounts in your name? If not, you will get banned very quickly.
Just wanted to post that in case you need it.

Good luck!